Telekinesis is the best sorcerer versus caster spell in the PHB.
If you see a Mage about to do something naughty, Combat Maneuver (grapple) him: your caster level + casting stat versus his BAB and Str mod. So the best of yours versus the worst of his. He'll end up grappled and he can't do squat.
If you see a Mage about to use a naughty wand or device, Combat Maneuver (disarm) him: again, your caster level + casting stat versus BAB and Str. He's disarmed and you've averted his naughty for another round.
If you see a Mage (or anyone, really) moving along a precipice, Combat Maneuver (Bull rush) them off. It will only be Casting stat versus Str or Dex, but you get to do this round after round.
You can also disarm people's stuff into your hands (though they get Will saves for this). You can fly, slowly. You can make terrific use of the discarded weapons of a battlefield*.
You can even take control of thrown or projectile weapons as they come towards you, albeit with a readied action; think how upset Wulfgar would be if you
Telekinesised his hammer just after he threw it, and it drifted gently into your hand. Awesome.
Telekinesis' true power is that one spell does all these things. This doesn't help wizards out that much, who can afford to stock up on utility spells, but it is absolutely priceless for Sorcerers. With this one spell you can fly, fight, disarm, grapple, lift heavy objects, attack with multiple weapons, and both pick your friends and pick your friends' nose. You can do all of this from Long range (which for a sorcerer means a minimum max-range of 800ft).
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*We were held at axepoint by 10 or so greataxe-wielding orcs and a cleric of Grummsh; the orcs were mostly surrounding me, the sorcerer. A
Fire-shield like effect later and the orcs were all down, and I still had a spell to cast.
Telekinesis all the greataxes to attack the cleric: 6 of them hit, causing 6d12 points of damage. I rolled well enough to take him down. I'm not saying it's always going to be a combat-ender, but the spell is useful is so many situations that a spell-hungry sorcerer can always find a use for it.